Reorganize classes

- Move base classes to its own package
- Move most logic out of MagiskActivity to MainActivity

app/src/main/java/com/topjohnwu/magisk/base/BasePreferenceFragment.kt

@@ -0,0 +1,56 @@
+package com.topjohnwu.magisk.base
+
+import android.annotation.SuppressLint
+import android.content.SharedPreferences
+import android.os.Bundle
+import android.view.LayoutInflater
+import android.view.View
+import android.view.ViewGroup
+import androidx.preference.*
+import androidx.recyclerview.widget.RecyclerView
+import org.koin.android.ext.android.inject
+
+abstract class BasePreferenceFragment : PreferenceFragmentCompat(),
+    SharedPreferences.OnSharedPreferenceChangeListener {
+
+    protected val prefs: SharedPreferences by inject()
+    protected val activity get() = requireActivity() as MagiskActivity<*, *>
+
+    override fun onCreateView(
+        inflater: LayoutInflater,
+        container: ViewGroup?,
+        savedInstanceState: Bundle?
+    ): View? {
+        val v = super.onCreateView(inflater, container, savedInstanceState)
+        prefs.registerOnSharedPreferenceChangeListener(this)
+        return v
+    }
+
+    override fun onDestroyView() {
+        prefs.unregisterOnSharedPreferenceChangeListener(this)
+        super.onDestroyView()
+    }
+
+    private fun setAllPreferencesToAvoidHavingExtraSpace(preference: Preference) {
+        preference.isIconSpaceReserved = false
+        if (preference is PreferenceGroup)
+            for (i in 0 until preference.preferenceCount)
+                setAllPreferencesToAvoidHavingExtraSpace(preference.getPreference(i))
+    }
+
+    override fun setPreferenceScreen(preferenceScreen: PreferenceScreen?) {
+        if (preferenceScreen != null)
+            setAllPreferencesToAvoidHavingExtraSpace(preferenceScreen)
+        super.setPreferenceScreen(preferenceScreen)
+    }
+
+    override fun onCreateAdapter(preferenceScreen: PreferenceScreen?): RecyclerView.Adapter<*> =
+            object : PreferenceGroupAdapter(preferenceScreen) {
+                @SuppressLint("RestrictedApi")
+                override fun onPreferenceHierarchyChange(preference: Preference?) {
+                    if (preference != null)
+                        setAllPreferencesToAvoidHavingExtraSpace(preference)
+                    super.onPreferenceHierarchyChange(preference)
+                }
+            }
+}